Just an fyi, just because someone else has something saved to their tree does not mean that their research is right. Always, double check and triple check sources. They've got to be somewhere. Problem is that she was born shortly before Civil War, so the possibility of being a slave is high. But, many slave records are better than records for others.
Go back to where you last left off, I think you said this was a 2 great grandmother? If so go back to great grandmother or if only 1 great go back to grandmother, look for her and siblings in all census indexes. Many times family stuck together or followed each other. Look at all indexes not just census, such as burials in all parishes and in any other state. Tedious I know, but you might just find them that way.